Method for recovering polyethylene glycol terephthalate from retired photovoltaic module backboard

Abstract

The invention belongs to the technical field of resource circulation, and mainly relates to a method for recovering polyethylene glycol terephthalate from a retired photovoltaic module backboard. The method comprises the following steps: after crushing a laminated part without an aluminum frame and a junction box, mixing the crushed laminated part with an alkaline alcohol solution to obtain a fluorine-containing backboard; and mixing the fluorine-containing back plate with a binary eutectic solvent, and carrying out heating reaction to obtain the fluorine film and PET (Polyethylene Terephthalate). According to the method, the eutectic solvent is selected as a selective separation solvent, and the binder impurities in the backboard composite material are selectively dissociated through temperature regulation and control, so that complete stripping and high-purity recovery of the PET layer are realized. The separation method is safe, efficient, simple to operate and environment-friendly, and provides a safe and sustainable technical route for recycling the PET material in the retired photovoltaic module.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of resource recycling, and mainly relates to a method for recovering polyethylene terephthalate from a retired photovoltaic module backboard. BACKGROUND

[0002] With the rapid development of the photovoltaic industry, the amount of retired photovoltaic modules is increasing year by year, and their recycling has become a difficult problem to be solved in the industry. In the recycling process of the modules, the efficient and green separation of the backboard is one of the key technical bottlenecks. The photovoltaic backboard is usually composed of a single or double fluorine film (such as polyvinylidene fluoride and polyvinyl fluoride) and a polyethylene terephthalate (PET) layer bonded by an ethylene-vinyl acetate copolymer (EVA).

[0003] Retired backboards are usually disposed by landfilling and incineration. Since the fluorine film has an exceptionally stable carbon-fluorine structure, it is difficult to degrade. If landfilling is used, the fluorine component is difficult to degrade, which seriously pollutes the land resources. If incineration or thermal treatment is used, toxic gases such as hydrogen fluoride may be generated, which may cause acid rain, greenhouse effect and human fluorine poisoning. In addition, a large number of researches on recycling methods are based on chemical methods for fine recycling, but the reaction process requires high temperature and high pressure, and the recycling cycle is long, the process is complex and the efficiency is low. At present, the recycling of the backboard needs end-of-pipe treatment to reduce the environmental impact of the three wastes, which increases the recycling cost, reduces the economic benefit, and is not sufficient to meet the large-scale resource demand for polyethylene terephthalate.

[0004] Therefore, it is urgent to develop a recycling technology for efficiently separating the components of the backboard. SUMMARY

[0005] In order to overcome the problems in the prior art, the present application provides a method for recovering polyethylene terephthalate from a retired photovoltaic module backboard, which uses a green solvent system to rapidly and efficiently separate polyethylene terephthalate and fluorine film under specific conditions, realizes the extraction and separation of waste polyethylene terephthalate in photovoltaic modules, and speeds up the resource process of waste polyethylene terephthalate.

[0006] In an embodiment of the present application, the present application provides a method for recovering polyethylene terephthalate from a retired photovoltaic module backboard, which comprises the following steps: S1, disassembling the retired photovoltaic module to remove the aluminum frame and junction box to obtain a laminated piece, and then crushing the laminated piece and mixing it with an alkaline alcohol solution for reaction to separate and obtain a backboard and a waste liquid; S2, mixing the backboard with a binary eutectic solvent, heating and reacting, and then separating to obtain a fluorine film and a polyethylene terephthalate, wherein the fluorine film floats on the upper layer of the solution, and the polyethylene terephthalate sinks at the bottom of the solution.

[0007] As an optional implementation, the size of the crushed laminated piece in step S1 is less than or equal to 3cm*3cm.

[0008] As an optional implementation, the mass-volume ratio of the crushed laminated piece to the alkaline alcohol solution in step S1 is 50-120g:500mL.

[0009] As an optional implementation, the alkali in the alkaline alcohol solution is at least one of sodium hydroxide and potassium hydroxide, the alcohol in the alkaline alcohol solution is at least one of ethanol and ethylene glycol, and the concentration of the alkaline alcohol solution is 0.2-0.5mol / L.

[0010] As an optional implementation, the mixing reaction condition in step S1 is: The reaction temperature is 60-80℃, and the reaction time is 0.25h-0.5h.

[0011] As an optional implementation, the binary deep eutectic solvent in step S2 is composed of a hydrogen bond acceptor and a hydrogen bond donor, and the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:1-4.

[0012] As an optional implementation, the binary deep eutectic solvent in step S2 is one or more of a binary deep eutectic solvent composed of a hydrogen bond acceptor choline and a hydrogen bond donor oxalic acid, a binary deep eutectic solvent composed of a hydrogen bond acceptor choline chloride and a hydrogen bond donor urea, a binary deep eutectic solvent composed of a hydrogen bond acceptor choline chloride and a hydrogen bond donor imidazole, a binary deep eutectic solvent composed of a hydrogen bond acceptor choline chloride and a hydrogen bond donor malonic acid, a binary deep eutectic solvent composed of a hydrogen bond acceptor choline chloride and a hydrogen bond donor ethylene glycol, and a binary deep eutectic solvent composed of a hydrogen bond acceptor choline chloride and a hydrogen bond donor 1,4-butanediol.

[0013] As an optional implementation, the mass-volume ratio of the back plate to the binary deep eutectic solvent in step S2 is 20-200g:500mL.

[0014] As an optional implementation, the heating reaction condition in step S2 is: The reaction temperature is 150-240℃, and the reaction time is 1-15h.

[0015] As an optional implementation, the method further comprises recycling the alcohol by distillation and condensation of the waste liquid obtained in step S1.

[0016] Compared with the prior art, the method has the following beneficial effects: (1) The present application first separates the back plate from other components by an alkaline alcohol solution, then uses a eutectic solvent as a green solvent, realizes the efficient and selective dissolution of the EVA adhesive through the synergistic effect of hydrogen bond donors and hydrogen bond acceptors, and at the same time avoids the damage to the fluorine film and the polyethylene terephthalate (PET) film, without the need for end-of-life management, significantly reducing the environmental pollution risk in the recycling process.

[0017] (2) The reaction in the present application can be carried out at normal pressure, the required heating temperature is low, after the reaction, the fluorine film floats on the surface of the solution, the EVA adhesive is dissociated in the solvent system, and the polyethylene terephthalate (PET) is settled at the bottom of the solution, the operation is simple, and the separation and further recovery are easy to realize. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings described below are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0019] Figure 1 The DSC curve of the PET recovered from the back plate of the decommissioned photovoltaic module provided by the embodiments of the present application; a) is the PET film recovered from example 7; b) is the PET film recovered from example 1. DETAILED DESCRIPTION In order to facilitate the understanding of the present application, the following will combine the drawings of the specification and the preferred embodiments to make a more comprehensive and detailed description of the present application, but the protection scope of the present application is not limited to the following specific embodiments.

[0020] Unless otherwise defined, all professional terms used in the following have the same meaning as generally understood by those skilled in the art. The professional terms used in this paper are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present application.

[0021] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0022] The present application provides a method for recovering polyethylene terephthalate from the back plate of a decommissioned photovoltaic module, wherein the photovoltaic module comprises glass, cell layer, fluorine-containing back plate and aluminum frame junction box and other accessories, and the specific recovery method comprises the following steps: Step S1 carries out the assembly unpacking to obtain the backboard, the specific method is: the retired photovoltaic assembly is removed to obtain the laminated part, and then the laminated part is broken to a particle size of less than or equal to 3cm*3cm, the broken laminated part is mixed with an alkaline alcohol solution, stirred and reacted at a temperature of 60~80℃ for 0.25h~0.5h, after the reaction is completed, the backboard floats on the waste liquid, and other parts sink at the bottom of the waste liquid, and the backboard and the waste liquid are separated. The alkali in the alkaline alcohol solution is at least one of sodium hydroxide and potassium hydroxide, the alcohol in the alkaline alcohol solution is at least one of ethanol and ethylene glycol, the concentration of the alkaline alcohol solution is 0.2~0.5mol / L. The mass-volume ratio of the laminated part and the alkaline alcohol solution is 50~120g:500mL. The above waste liquid can be recycled by heating distillation and condensation of alcohol.

[0023] Step S2 carries out PET separation, the above backboard is mixed with a binary deep eutectic solvent according to a mass-volume ratio of 50~120g:500mL, heated and reacted at a temperature of 150~240℃ for 1~15h, after the reaction is completed, the fluorine film floats on the upper layer of the reaction solution, the EVA layer in the backboard is dissolved in the reaction solution, and the PET sinks at the bottom of the reaction solution, and the PET is separated. The binary deep eutectic solvent is composed of a hydrogen bond acceptor and a hydrogen bond donor, and the molar ratio of the hydrogen bond acceptor and the hydrogen bond donor is 1:1~4. The binary deep eutectic solvent specifically includes: a binary deep eutectic solvent (DES ChCl-OA ) composed of a hydrogen bond acceptor choline chloride and a hydrogen bond donor oxalic acid, a binary deep eutectic solvent (DES ChCl-Urea ) composed of a hydrogen bond acceptor choline chloride and a hydrogen bond donor urea, a binary deep eutectic solvent (DES ChCl-IM ) composed of a hydrogen bond acceptor choline chloride and a hydrogen bond donor imidazole, a binary deep eutectic solvent (DES ChCl-MA ) composed of a hydrogen bond acceptor choline chloride and a hydrogen bond donor malonic acid, a binary deep eutectic solvent (DES ChCl-EG ) composed of a hydrogen bond acceptor choline chloride and a hydrogen bond donor ethylene glycol, and a binary deep eutectic solvent (DES ChCl-BD ) composed of a hydrogen bond acceptor choline chloride and a hydrogen bond donor 1,4-butanediol.

[0024] It should be understood that one or a combination of the two of physical stirring or ultrasonic treatment is carried out in the above two-step reaction process to accelerate the reaction rate.

[0025] The embodiments of the present application will be described in detail below, the embodiments are implemented on the premise of the technical scheme of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following embodiments.

[0026] Example 1 The embodiment provides a method for recycling polyethylene terephthalate (PET) from a backboard of a decommissioned photovoltaic module, and separates and recycles PET and a fluorine film according to the following steps: Step S1, a photovoltaic module is obtained after mechanical removal of an aluminum frame and a junction box, is broken into small 3cm*3cm samples, 100.47g of the samples are added into a 500mL sodium hydroxide ethanol solution with a concentration of 0.4mol / L for reaction, the heating temperature is 80℃, and after 0.25h of reaction, the backboard and other parts of the photovoltaic laminate are separated, the solid product is cleaned and dried, and then weighed, and a total of 4.71g of the backboard and 94.83g of the bottom precipitate are recycled.

[0027] Step S2, the recycled 4.71g of the backboard is put into a DES of a hydrogen bond acceptor choline chloride and a hydrogen bond donor oxalic acid with a molar ratio of 1:2 ChCl-OA with a heating temperature of 170℃, after 10h of reaction, the fluorine film floats in the solution, the EVA enters the solvent, and the PET film sinks at the bottom of the solution.

[0028] A total of 3.02g of the PET film and 1.66g of the fluorine film are recycled.

[0029] Embodiment 2 The embodiment provides a method for recycling polyethylene terephthalate (PET) from a backboard of a decommissioned photovoltaic module, and separates and recycles PET and a fluorine film according to the following steps: Step (1): a photovoltaic module is obtained after mechanical removal of an aluminum frame and a junction box, is broken into small 3cm*3cm samples, 99.82g of the samples are added into a 500mL potassium hydroxide ethanol solution with a concentration of 0.4mol / L for reaction, the heating temperature is 75℃, and after 0.5h of reaction, the backboard and other parts of the photovoltaic laminate are mechanically separated, the solid product is cleaned and dried, and then weighed, and a total of 4.53g of the backboard and 94.97g of the bottom precipitate are recycled.

[0030] Step (2): the recycled 4.53g of the backboard is put into a DES of a hydrogen bond acceptor choline chloride and a hydrogen bond donor urea with a molar ratio of 1:2 ChCl-Urea with a heating temperature of 150℃, after 12h of reaction, the fluorine film floats in the solution, the EVA enters the solvent, and the PET film sinks at the bottom of the solution.

[0031] Embodiment 3 The embodiment provides a method for recycling polyethylene terephthalate (PET) from a backboard of a decommissioned photovoltaic module, and separates and recycles PET and a fluorine film according to the following steps: Step (1): Take a photovoltaic module, mechanically remove the aluminum frame and junction box to obtain a photovoltaic laminate, crush it into small samples of 3 cm * 3 cm, take 107.12 g of the sample and add it to a 0.5 mol / L potassium hydroxide ethylene glycol solution with a volume of 1000 mL for reaction, the heating temperature is 60°C, after 0.25h of reaction, the backboard and other parts of the photovoltaic laminate can be mechanically separated, the solid product is washed and dried, and then weighed, a total of 4.99 g of backboard and 101.96 g of bottom precipitate are recovered.

[0032] Step (2): Put the recovered 4.99 g of backboard into a DES ChCl-IM with a molar ratio of hydrogen bond acceptor choline chloride to hydrogen bond donor imidazole of 1:4, with a volume of about 50 mL, the heating temperature is 220°C, after 5h of reaction, the fluorine film floats in the solution, the EVA enters the solvent, and the PET film sinks at the bottom of the solution.

[0033] Finally, a total of 3.58 g of PE film T and 1.40 g of fluorine film are recovered.

[0034] Example 4 This example provides a method for recycling polyethylene terephthalate (PET) from the backboard of a retired photovoltaic module, which separates and recovers PET and fluorine film according to the following steps, and recovers each component: Step (1): Take a photovoltaic module, mechanically remove the aluminum frame and junction box to obtain a photovoltaic laminate, crush it into small samples of 3 cm * 3 cm, take 107.12 g of the sample and add it to a 0.5 mol / L potassium hydroxide ethylene glycol solution with a volume of 1000 mL for reaction, the heating temperature is 60°C, after 0.25h of reaction, the backboard and other parts of the photovoltaic laminate can be mechanically separated, the solid product is washed and dried, and then weighed, a total of 4.99 g of backboard and 101.96 g of bottom precipitate are recovered.

[0035] Step (2): Put the recovered 4.99 g of backboard into a DES ChCl-IM with a molar ratio of hydrogen bond acceptor choline chloride to hydrogen bond donor imidazole of 1:4, with a volume of about 50 mL, the heating temperature is 220°C, after 5h of reaction, the fluorine film floats in the solution, the EVA enters the solvent, and the PET film sinks at the bottom of the solution.

[0036] Finally, a total of 3.58 g of PE film T and 1.40 g of fluorine film are recovered.

[0037] Example 5 This example provides a method for recycling polyethylene terephthalate (PET) from the backboard of a retired photovoltaic module, which separates and recovers PET and fluorine film according to the following steps, and recovers each component: Step (1): Take a photovoltaic module, mechanically remove the aluminum frame and junction box to obtain a photovoltaic laminate, crush it into small samples of 3 cm * 3 cm, take 119.19 g of the sample and add it to a 500 mL volume of 0.5 mol / L sodium hydroxide ethylene glycol solution for reaction, the heating temperature is 70°C, after 0.5h of reaction, the backboard and other parts of the photovoltaic laminate can be mechanically separated, the solid product is washed and dried, and then weighed, a total of 5.40 g of backboard and 113.33 g of bottom precipitate are recovered.

[0038] Step (2): Put the recovered 5.40 g of backboard into a DES ChCl-BD with a molar ratio of 1:2 of hydrogen bond acceptor choline chloride and hydrogen bond donor 1,4-butanediol, the heating temperature is 160°C, after 10h of reaction, the fluorine film floats in the solution, the EVA enters the solvent, and the PET film sinks at the bottom of the solution.

[0039] Finally, a total of 3.50 g of PET film and 1.68 g of fluorine film are recovered.

[0040] Example 6 This example provides a method for recovering polyethylene terephthalate (PET) from the backboard of a retired photovoltaic module, which separates and recovers PET and fluorine film according to the following steps, and recovers each component: Step (1): Take a photovoltaic module, mechanically remove the aluminum frame and junction box to obtain a photovoltaic laminate, crush it into small samples of 3 cm * 3 cm, take 119.19 g of the sample and add it to a 500 mL volume of 0.5 mol / L sodium hydroxide ethylene glycol solution for reaction, the heating temperature is 70°C, after 0.5h of reaction, the backboard and other parts of the photovoltaic laminate can be mechanically separated, the solid product is washed and dried, and then weighed, a total of 5.40 g of backboard and 113.33 g of bottom precipitate are recovered.

[0041] Step (2): Put the recovered 5.40 g of backboard into a DES ChCl-BD with a molar ratio of 1:2 of hydrogen bond acceptor choline chloride and hydrogen bond donor 1,4-butanediol, the heating temperature is 160°C, after 10h of reaction, the fluorine film floats in the solution, the EVA enters the solvent, and the PET film sinks at the bottom of the solution.

[0042] Finally, a total of 3.50 g of PET film and 1.68 g of fluorine film are recovered.

[0043] Example 7 This example provides a method for recovering polyethylene terephthalate (PET) from the backboard of a retired photovoltaic module, which separates and recovers PET and fluorine film according to the following steps, and recovers each component: Step (1): Take a photovoltaic module, mechanically remove the aluminum frame and junction box to obtain a photovoltaic laminate, crush it into small pieces of 3cm*3cm, take 101.94g of the sample and add it to a 150mL volume of 0.2mol / L sodium hydroxide ethanol solution for reaction, the heating temperature is 60℃, after 0.25h of reaction, the backboard and other parts of the photovoltaic laminate can be mechanically separated, the solid product is washed and dried, and then weighed, a total of 2.83g of backboard and 99.09g of bottom precipitate are recovered.

[0044] Step (2): Put the recovered 2.83g of backboard into a DES of ChCl-OA with a molar ratio of hydrogen bond acceptor choline chloride to hydrogen bond donor oxalic acid of 1:2, with a volume of about 100mL, the heating temperature is 150℃, after 7.5h of reaction, the fluorine film floats in the solution, the EVA enters the solvent, and the PET film sinks at the bottom of the solution.

[0045] Finally, a total of 1.83g of PET film and 0.96g of fluorine film are recovered.

[0046] Example 8 This example provides a method for recycling polyethylene terephthalate (PET) from the backboard of a retired photovoltaic module, which separates and recovers PET and fluorine film according to the following steps, and recovers each component: Step (1): Take a photovoltaic module, mechanically remove the aluminum frame and junction box to obtain a photovoltaic laminate, crush it into small pieces of 2cm*1cm, take 83.17g of the sample and add it to a 150mL volume of 0.3mol / L sodium hydroxide ethanol solution for reaction, the heating temperature is 60℃, after 0.25h of reaction, the backboard and other parts of the photovoltaic laminate can be mechanically separated, the solid product is washed and dried, and then weighed, a total of 3.92g of backboard and 79.22g of bottom precipitate are recovered.

[0047] Step (2): Put the recovered 3.92g of backboard into a DES of ChCl-Urea with a molar ratio of hydrogen bond acceptor choline chloride to hydrogen bond donor urea of 1:2, with a volume of about 100mL, the heating temperature is 200℃, after 12h of reaction, the fluorine film floats in the solution, the EVA enters the solvent, and the PET film sinks at the bottom of the solution.

[0048] Finally, a total of 2.53g of PET film and 1.37g of fluorine film are recovered.

[0049] Example 9 This example provides a method for recycling polyethylene terephthalate (PET) from the backboard of a retired photovoltaic module, which separates and recovers PET and fluorine film according to the following steps, and recovers each component: Step (1): Take a photovoltaic module, mechanically remove the aluminum frame and junction box to obtain a photovoltaic laminate, crush it into small samples of 3cm*3cm, take 107.12g of the sample and add it to a 0.2mol / L potassium hydroxide ethylene glycol solution with a volume of 1000mL for reaction, the heating temperature is 80℃, after 0.5h of reaction, the backboard and other parts of the photovoltaic laminate can be mechanically separated, the solid product is washed and dried, and then weighed, a total of 4.99g of backboard and 101.96g of bottom precipitate are recovered.

[0050] Step (2): Put the recovered 4.99g backboard into a DES ChCl-IM with a molar ratio of 1:4 of hydrogen bond acceptor choline chloride and hydrogen bond donor imidazole with a volume of about 50mL, the heating temperature is 220℃, after 5h of reaction, the fluorine film floats in the solution, the EVA enters the solvent, and the PET film sinks at the bottom of the solution.

[0051] Finally, a total of 3.58g of PE film T and 1.40g of fluorine film are recovered.

[0052] Example 10 This example provides a method for recovering polyethylene terephthalate (PET) from the backboard of a retired photovoltaic module, which separates and recovers PET and fluorine film according to the following steps, and recovers each component: Step (1): Take a photovoltaic module, mechanically remove the aluminum frame and junction box to obtain a photovoltaic laminate, crush it into small samples of 3cm*3cm, take 107.12g of the sample and add it to a 0.2mol / L potassium hydroxide ethylene glycol solution with a volume of 1000mL for reaction, the heating temperature is 80℃, after 0.5h of reaction, the backboard and other parts of the photovoltaic laminate can be mechanically separated, the solid product is washed and dried, and then weighed, a total of 4.99g of backboard and 101.96g of bottom precipitate are recovered.

[0053] Step (2): Put the recovered 4.52g backboard into a DES ChCl-MA with a molar ratio of 1:1 of hydrogen bond acceptor choline chloride and hydrogen bond donor malonic acid with a volume of about 50mL, the heating temperature is 220℃, after 12h of reaction, the fluorine film floats in the solution, the EVA enters the solvent, and the PET film sinks at the bottom of the solution.

[0054] Finally, a total of 2.90g of PET film and 1.59g of fluorine film are recovered.

[0055] Example 11 This example provides a method for recovering polyethylene terephthalate (PET) from the backboard of a retired photovoltaic module, which separates and recovers PET and fluorine film according to the following steps, and recovers each component: Step (1): Take a photovoltaic module, mechanically remove the aluminum frame and junction box to obtain a photovoltaic laminate, crush it into small pieces of 3 cm * 3 cm, take 95.67 g of the sample and add it to a 500 mL volume of 0.3 mol / L sodium hydroxide ethylene glycol solution for reaction, the heating temperature is 60°C, after 0.25h of reaction, the backboard and other parts of the photovoltaic laminate can be mechanically separated, the solid product is washed and dried, and then weighed, a total of 4.49 g of backboard and 90.99 g of bottom precipitate are recovered.

[0056] Step (2): Put the recovered 4.49 g of backboard into a DES ChCl-BD with a molar ratio of 1:2 of hydrogen bond acceptor choline chloride and hydrogen bond donor 1,4-butanediol, the heating temperature is 190°C, after 12h of reaction, the fluorine film floats in the solution, the EVA enters the solvent, and the PET film sinks at the bottom of the solution.

[0057] Finally, a total of 2.67 g of PET film and 1.44 g of fluorine film are recovered.

[0058] Example 12 This example provides a method for recovering polyethylene terephthalate (PET) from the backboard of a retired photovoltaic module, which separates and recovers PET and fluorine film according to the following steps, and recovers each component: Step (1): Take a photovoltaic module, mechanically remove the aluminum frame and junction box to obtain a photovoltaic laminate, crush it into small pieces of 2 cm * 2 cm, take 90.78 g of the sample and add it to a 500 mL volume of 0.2 mol / L sodium hydroxide ethylene glycol solution for reaction, the heating temperature is 70°C, after 0.25h of reaction, the backboard and other parts of the photovoltaic laminate can be mechanically separated, the solid product is washed and dried, and then weighed, a total of 4.13 g of backboard and 85.78 g of bottom precipitate are recovered.

[0059] Step (2): Put the recovered 4.13 g of backboard into a DES ChCl-BD with a molar ratio of 1:2 of hydrogen bond acceptor choline chloride and hydrogen bond donor 1,4-butanediol, the heating temperature is 190°C, after 12h of reaction, the fluorine film floats in the solution, the EVA enters the solvent, and the PET film sinks at the bottom of the solution.

[0060] Finally, a total of 2.67 g of PET film and 1.44 g of fluorine film are recovered. Comparative Example 1 This example provides a method for recovering polyethylene terephthalate (PET) from the backboard of a retired photovoltaic module, which separates and recovers PET and fluorine film according to the following steps, and recovers each component: Step (1): Take a piece of photovoltaic module, after mechanical removal of the aluminum frame and junction box, get photovoltaic laminates, broken into 5cm*5cm large block samples, take 52.78g large block samples into the concentration of 0.3mol / L sodium hydroxide ethylene glycol solution with a volume of 500mL for reaction, heating temperature is 60℃, after 0.25h reaction, the backplane cannot be effectively separated from the module.

[0061] Comparative Example 2 This comparative example provides a method for recovering polyethylene terephthalate (PET) from the backplane of a retired photovoltaic module, according to the following steps to separate and recover PET and fluorine film, and recover each component thereof: Step (1): Take a piece of photovoltaic module, after mechanical removal of the aluminum frame and junction box, get photovoltaic laminates, broken into 3cm*3cm small block samples, take 103.97g samples into the concentration of 0.3mol / L sodium hydroxide aqueous solution with a volume of 500mL for reaction, heating temperature is 60℃, after 0.25h reaction, the backplane cannot be effectively separated from the module.

[0062] Comparative Example 3 This comparative example provides a method for recovering polyethylene terephthalate (PET) from the backplane of a retired photovoltaic module, according to the following steps to separate and recover PET and fluorine film, and recover each component thereof: Step (1): Take a piece of photovoltaic module, after mechanical removal of the aluminum frame and junction box, get photovoltaic laminates, broken into 3cm*3cm small block samples, take 103.97g samples into the concentration of 0.3mol / L sodium hydroxide aqueous solution with a volume of 500mL for reaction, heating temperature is 60℃, after 0.5h reaction, the backplane cannot be effectively separated from the module.

[0063] Comparative Example 4 This comparative example provides a method for recovering polyethylene terephthalate (PET) from the backplane of a retired photovoltaic module, according to the following steps to separate and recover PET and fluorine film, and recover each component thereof: Step (1): Take a piece of photovoltaic module, after mechanical removal of the aluminum frame and junction box, get photovoltaic laminates, broken into 3cm*3cm small block samples, take 74.57g samples into the concentration of 0.3mol / L sodium hydroxide aqueous solution with a volume of 500mL for reaction, heating temperature is 60℃, after 0.5h reaction, the backplane cannot be effectively separated from the module.

[0064] Comparative Example 5 Step (1): Take a photovoltaic module, mechanically remove the aluminum frame and junction box to obtain a photovoltaic laminate, break it into small 3cm*3cm samples, weigh 75.37g of the sample and add it to a 500mL volume of 0.3mol / L potassium hydroxide ethanol solution for reaction, the heating temperature is 75℃, after 0.5h of reaction, the backboard and other parts of the photovoltaic laminate can be mechanically separated, the solid product is washed and dried, and then weighed, a total of 3.56g of backboard and 71.25g of bottom precipitate are recovered.

[0065] Step (2): Put the recovered 3.56g backboard into a DES ChCl-OA with a molar ratio of hydrogen bond acceptor choline chloride to hydrogen bond donor oxalic acid of 1:2, the heating temperature is 50℃, after 5h of reaction, the PET in the backboard cannot be effectively separated from the fluorine film.

[0066] Comparative Example 6 Step (1): Take a photovoltaic module, mechanically remove the aluminum frame and junction box to obtain a photovoltaic laminate, break it into small 3cm*3cm samples, weigh 110.37g of the sample and add it to a 500mL volume of 0.3mol / L sodium hydroxide ethanol solution for reaction, the heating temperature is 75℃, after 0.5h of reaction, the backboard and other parts of the photovoltaic laminate can be mechanically separated, the solid product is washed and dried, and then weighed, a total of 5.20g of backboard and 105.06g of bottom precipitate are recovered.

[0067] Step (2): Put the recovered 5.20g backboard into a DES ChCl-OA with a molar ratio of hydrogen bond acceptor choline chloride to hydrogen bond donor oxalic acid of 1:2, the heating temperature is 100℃, after 7.5h of reaction, the PET in the backboard cannot be effectively separated from the fluorine film.

[0068] Comparative Example 7 Step (1): Take a photovoltaic module, mechanically remove the aluminum frame and junction box to obtain a photovoltaic laminate, break it into small 3cm*3cm samples, weigh 123.57g of the sample and add it to a 500mL volume of 0.3mol / L sodium hydroxide ethanol solution for reaction, the heating temperature is 75℃, after 0.5h of reaction, the backboard and other parts of the photovoltaic laminate can be mechanically separated, the solid product is washed and dried, and then weighed, a total of 5.79g of backboard and 117.78g of bottom precipitate are recovered.

[0069] Step (2): Put the recovered 5.79g backboard into a DES ChCl-OA with a molar ratio of hydrogen bond acceptor choline chloride to hydrogen bond donor oxalic acid of 1:2, the heating temperature is 100℃, after 7.5h of reaction, the PET in the backboard cannot be effectively separated from the fluorine film.

[0070] Comparative Example 8 Step (1): Take a photovoltaic module, mechanically remove the aluminum frame and junction box to obtain a photovoltaic laminate, break it into small 3cm*3cm samples, weigh 70.96g of the sample and add it to a 500mL volume of 0.3mol / L sodium hydroxide ethanol solution for reaction, the heating temperature is 75℃, after 0.5h of reaction, the backboard and other parts of the photovoltaic laminate can be mechanically separated, the solid product is washed and dried, and then weighed, a total of 3.35g of backboard and 67.40g of bottom precipitate are recovered.

[0071] Step (2): Put the recovered 3.35g backboard into a DES ChCl-OA with a molar ratio of hydrogen bond acceptor choline chloride to hydrogen bond donor oxalic acid of 1:2, the volume is about 50mL, the heating temperature is 120℃, after 7.5h of reaction, the PET in the backboard cannot be effectively separated from the fluorine film.

[0072] Comparative Example 9 Step (1): Take a photovoltaic module, mechanically remove the aluminum frame and junction box to obtain a photovoltaic laminate, break it into small 3cm*3cm samples, weigh 70.96g of the sample and add it to a 500mL volume of 0.3mol / L sodium hydroxide ethanol solution for reaction, the heating temperature is 75℃, after 0.5h of reaction, the backboard and other parts of the photovoltaic laminate can be mechanically separated, the solid product is washed and dried, and then weighed, a total of 3.35g of backboard and 67.40g of bottom precipitate are recovered.

[0073] Step (2): Put the recovered 3.35g backboard into a DES ChCl-OA with a molar ratio of hydrogen bond acceptor choline chloride to hydrogen bond donor oxalic acid of 1:2, the volume is about 50mL, the heating temperature is 120℃, after 7.5h of reaction, the PET in the backboard cannot be effectively separated from the fluorine film.

[0074] For better comparison, the reaction conditions and results of each example and comparative example are shown in Tables 1, 2, 3, and 4.

[0075] Table 1 Reaction conditions and results of Examples 1-6 As can be seen from Table 1, Examples 1-6 use high-concentration alkaline alcohol solution to achieve separation of the backboard in the module at a lower temperature and in a short time. Under suitable sample size and solid-liquid ratio, high-efficiency separation can be achieved by 0.4mol / L alkaline alcohol solution.

[0076] Table 2 Specific reaction conditions and results of Examples 7-12 As can be further seen from Tables 1 and 2, the eutectic solvent can begin to effectively separate the fluorine film at about 150℃, and the DESChCl-OA The effect is obviously better than other deep eutectic solvents. To further analyze the residual situation of the adhesive EVA under the conditions of Example 1 and Example 7, the recovered product PET film was characterized by DSC, and the results are shown in Figure 1 The thermal absorption peak of EVA in the figure disappears, and Example 1 more effectively removes the EVA adhesive in the back plate.

[0077] Table 3 Specific reaction conditions and results of Comparative Examples 1-4 The reaction conditions in Table 3 did not effectively separate the back plate and the assembly. Compared with Example 11, it can be found that in Comparative Example 1, the size is larger, and the alkaline alcohol solution cannot effectively penetrate to dissociate the adhesive; in Comparative Examples 2 or 3, after replacing the solvent with water, the dissociation effect drops sharply; in Comparative Example 4, after using pure to dissociate, even at a higher reaction temperature and longer reaction time, the back plate cannot be effectively unsealed.

[0078] Table 4 Specific reaction conditions and results of Comparative Examples 5-9 Under the reaction conditions in Table 4, the fluorine film and the back plate were not separated. According to Tables 1, 2 and 4, it can be seen that the DES ChCl-OA The reaction conditions of 150℃ and 7.5h can effectively separate PET and fluorine film.

[0079] The above is a further detailed description of the present application in combination with specific preferred embodiments, and cannot be considered as limiting the specific implementation of the present application to these descriptions. For ordinary skilled persons in the art to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, which should be considered as belonging to the protection scope of the present application.

Claims

1. A method for recovering polyethylene terephthalate from the backsheet of decommissioned photovoltaic modules, characterized in that, The method includes the following steps: S1. Remove the aluminum frame and junction box from the retired photovoltaic module to obtain the laminate, then crush the laminate and mix it with an alkaline alcohol solution to react and separate it to obtain the backsheet and waste liquid. S2. The backplate is mixed with a binary eutectic solvent, heated and reacted to obtain a fluorinated membrane and polyethylene terephthalate. The fluorinated membrane floats on the upper layer of the solution, and the polyethylene terephthalate sinks to the bottom of the solution.

2. The method for recovering polyethylene terephthalate from the backsheet of decommissioned photovoltaic modules according to claim 1, characterized in that, In step S1, the particle size of the laminate after crushing is less than or equal to 3cm*3cm.

3. The method for recovering polyethylene terephthalate from the backsheet of decommissioned photovoltaic modules according to claim 1, characterized in that, In step S1, the mass-to-volume ratio of the crushed laminate to the alkaline alcohol solution is 50-120g:500mL.

4. The method for recovering polyethylene terephthalate from the backsheet of decommissioned photovoltaic modules according to claim 1, characterized in that, The alkali in the alkaline alcohol solution is at least one of sodium hydroxide and potassium hydroxide, and the alcohol in the alkaline alcohol solution is at least one of ethanol and ethylene glycol. The concentration of the alkaline alcohol solution is 0.2~0.5 mol / L.

5. The method for recovering polyethylene terephthalate from the backsheet of decommissioned photovoltaic modules according to claim 1, characterized in that, The conditions for the mixing reaction in step S1 are as follows: The reaction temperature is 60~80℃; the reaction time is 0.25h~0.5h.

6. The method for recovering polyethylene terephthalate from the backsheet of decommissioned photovoltaic modules according to claim 1, characterized in that, In step S2, the binary eutectic solvent is composed of hydrogen bond acceptors and hydrogen bond donors, with a molar ratio of 1:1 to 4.

7. The method for recovering polyethylene terephthalate from the backsheet of decommissioned photovoltaic modules according to claim 1, characterized in that, In step S2, the binary eutectic solvent is one or more of the following: a binary eutectic solvent composed of hydrogen bond acceptor choline and hydrogen bond donor oxalic acid; a binary eutectic solvent composed of hydrogen bond acceptor choline chloride and hydrogen bond donor urea; a binary eutectic solvent composed of hydrogen bond acceptor choline chloride and hydrogen bond donor imidazole; a binary eutectic solvent composed of hydrogen bond acceptor choline chloride and hydrogen bond donor malonic acid; a binary eutectic solvent composed of hydrogen bond acceptor choline chloride and hydrogen bond donor ethylene glycol; and a binary eutectic solvent composed of hydrogen bond acceptor choline chloride and hydrogen bond donor 1,4-butanediol.

8. The method for recovering polyethylene terephthalate from the backsheet of decommissioned photovoltaic modules according to claim 1, characterized in that, In step S2, the mass-to-volume ratio of the backplate to the binary eutectic solvent is 20-200g:500mL.

9. The method for recovering polyethylene terephthalate from the backsheet of decommissioned photovoltaic modules according to claim 1, characterized in that, The conditions for the heating reaction in step S2 are as follows: The reaction temperature is 150~240℃, and the reaction time is 1~15h.

10. The method for recovering polyethylene terephthalate from the backsheet of a decommissioned photovoltaic module according to claim 1, characterized in that, The method further includes: The waste liquid obtained in step S1 is distilled, condensed, and the alcohol is recovered for recycling.

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